Modeling How to solidify or scale an irregular shape, maybe flip vertices?
You have converted it to a mesh, and then extruded the points in edit mode.
Another way you could try is to keep it as a bezier curve and remain in object mode and go to
object data properties&gt;geometry&gt;extrude
You can set the bevel and offset at that point, and then convert it to mesh afterwards.
This seems to result in very smooth geometry.